1. Field of the Invention
The present invention relates to medical devices with inflatable retention balloons and more particularly to an apparatus for preventing over inflation of the catheter retention balloons in a fecal management system or an endotracheal rube.
2. Description of Prior Art Including Information
Fecal management systems, such as the one disclosed in U.S. Pat. No. 8,016,816, issued Sep. 13, 2011 to Christopher C. Gregory, which patent is incorporated herein by reference, are known in the art. The system disclosed in the Gregory patent is a medical appliance formed of an elongated flexible tubular element or catheter having a distal end designed to be introduced into a body cavity, such as the rectum through the anal sphincter. The proximal end of catheter is connected to a receptacle for the collection of fecal waste.
Affixed to the exterior surface of the distal end of the catheter is an inflatable balloon which serves to retain the distal end of the catheter within the body cavity. The balloon is inflated to a suitable diameter with fluid, such as air, water or saline, through a fluid supply tube or lumen, after it is inserted into the body cavity. The supply lumen is connected to a source of pressurized inflation fluid, such as a syringe. The syringe is also used to withdraw the inflation fluid through the supply lumen, to deflate the balloon.
A second lumen may be provided to deliver irrigation fluid to the body cavity. One end of irrigation lumen extends through a port in the distal end of the catheter. The other end is connected to a source of irrigation fluid.
The distal end of the catheter and the retention balloon are both made entirely of soft, compliant material, for example, silicone, so as not to injure any body tissue.
The retention balloon surrounds the distal end of the catheter and preferably has a toroidal shape when fully inflated. The wall of the balloon may be fabricated in its fully inflated shape of material that allows the balloon to be inflated to its final shape.
Fecal management systems using an inflated retention balloon must be used carefully because they can create too much pressure on the rectal tissue if the retention balloon is over inflated. That pressure is a result of the balloon being filled with a volume of fluid greater the space available in the body cavity. Accordingly, all fecal management systems have an indicated maximum volume for the retention balloon that each manufacturer has established as safe. However, this maximum balloon volume can be exceeded by over inflating the balloon, resulting in damage to the soft tissue surrounding the balloon.
Similarly, endotracheal tubes have affixed to the exterior surface of the distal end of the catheter an inflatable balloon which serves to retain the distal end of the catheter within the body cavity and create an air seal to the trachea. The balloon is inflated to a suitable diameter with fluid, such as air, through a fluid supply tube or lumen, after it is inserted into the trachea. The supply lumen is connected to a source of pressurized inflation fluid, such as a syringe. The syringe is also used to withdraw the inflation fluid through the supply lumen, to deflate the balloon. In an endotracheal tube, the retention balloon surrounds the distal end of the catheter and preferably has a toroidal shape when fully inflated. The wall of the balloon may be fabricated in its fully inflated shape of material that allows the balloon to be inflated to its final shape.
Endotracheal systems using an inflated retention balloon must be used carefully because they can create too much pressure on the mucosal tissue in the trachea if the retention balloon is over inflated. That pressure is a result of the balloon being filled with a volume of fluid greater the space available in the trachea. Accordingly, all endotracheal tubes have an indicated maximum volume for the retention balloon that each manufacturer has established as safe or pressure monitoring mechanisms. However, this maximum balloon volume or pressure can be exceeded by over inflating the balloon, resulting in damage to the soft tissue surrounding the balloon.
Although one commercially available fecal management system (Flexi-Seal® SIGNAL™ FMS) can be obtained with an indicator that tells the clinician when the balloon is properly filled, there continue to be cases where clinicians have initially over inflated the retention balloon, or have added more fluid to the balloon after the catheter has been in use, resulting in a potentially hazardous situation.
Another disclosed system employs a catheter with a pressure relief valve. However, that approach has not proved to be practical because in use there are frequently brief periods of muscle contraction in the rectum that result in high pressure in the balloon. In the trachea there are periods of high pressure during the respiratory cycle. If the inflation fluid were allowed to escape under those high pressure conditions, the retention of the device would be compromised and the catheter expelled or the seal lost. Accordingly, neither of these approaches has proved successful.
Another possible approach to the over inflation problem would be to electronically measure the amount of inflation fluid provided to the balloon. Accurate measurement of the volume of a flowing fluid through a tube requires the measurement of the flow rate of the fluid and of the time during which the fluid is flowing. Those values can then be multiplied to calculate the total volume of fluid that has passed through the tube. This is typically done through real time electronic measurement of the flow rate which utilizes the cooling ability of the fluid across a heated probe, and a microprocessor completing the calculations.
For prevention of the delivery of too much fluid, the result of this calculation then has to control a valve or actuate an alarm to prevent additional fluid from being added to the balloon. Clearly, devices using this method of calculating the amount of fluid used to inflate the balloon are complex and costly. Moreover, they have difficulty in taking into account the fact that the fluid can and needs to be able to be withdrawn from the balloon, as well as provided to the balloon, because they cannot easily differentiate between the flow directions. Simpler and less expensive options are desirable, and are provided by the present invention.
The present invention relates to apparatus designed for use as part of a fecal management system or endotracheal tube of the type including a catheter with an inflatable retention balloon. The apparatus is utilized as part of the fluid inflation system and several different device configurations and modes of operation are disclosed which prevent over inflation of the retention balloon by limiting the flow of inflation fluid to the catheter balloon to a specific volume or pressure.